The retired engineer had spent two years battling Multiple System
Atrophy, a rare progressive neurological disorder that attacks the
brain and nervous system.

Mr Sinclair is understood to have gone to Switzerland when his body began to shut down.

He is said to have travelled with a 48-year-old man, whose identity
has not been released but is believed to have been a close friend. The
man was arrested over allegations of assisting a suicide and released
on bail.

He was held with Janet Grieves, 47, who was also bailed. Mrs
Grieves, of South Shields, Tyne and Wear, is thought to have known
about Mr Sinclair’s wish to die, but refused to travel to Zurich.

The pair looked after him at his house in South Shields before he went into a care home last year.

Mr Sinclair is understood to have died on July 28, leaving an estate
worth an estimated £100,000. He had previously lived alone after his
wife, Monica, died of leukaemia ten years ago. Friends said he never
fully recovered from losing her.

Last night it emerged that a team of health professionals held an
urgent meeting in January after Mr Sinclair threatened to kill himself.
At the meeting – attended by legal, medical and social services
representatives – it was revealed the pensioner had told staff at
Stapleton House nursing home in Jarrow he intended to go to Switzerland
to end his life.

Arrests: Two people have been questioned by police over the death of Mr Sinclair, who lived at this house South Shields

Despite the threats, however, Mr Sinclair was allowed to leave the
home in a taxi at the end of June. It is not known if the staff were
aware he was travelling to Zurich.

A death notice in a local newspaper said Mr Sinclair died ‘peacefully and with dignity’.

The pensioner’s daughter Helen said she had not known about his suicide plan.

Miss Sinclair, 41, of Darlington, said: ‘My father was a popular and
caring man. He was devastated by the loss of his wife, my mother, and
since his illness decided to end his life with dignity in the manner of
his choosing.

‘Although this was disturbing and upsetting for me, I respect his decision.’

Taboo: Euthanasia is legal in Switzerland at centres like the Dignitas Clinic in Zurich

Neighbours in South Shields, where Mr Sinclair lived for two decades, paid tribute to a ‘delightful man’ .

Joe Bolam, 68, said: ‘The whole street was devastated. But if it’s true that he made the decision to take his own life, then I have no problem with that. It’s his life and his choice.’

Mr Sinclair’s body was flown back to the UK for his funeral last week.

But there was criticism from Father Michael Weymes, of St Bede’s and Holy Rosary Roman Catholic Churches, who carried out the service.

He said yesterday: ‘The Church does not condone, in any way, someone taking their own life. If it is true that two people helped him, then that is seriously wrong. Disability is not an excuse to take your own life.’

While it is not illegal to assist a suicide in Switzerland, it remains a crime in the UK.

South Tyneside Council confirmed a ‘safeguarding meeting’ was held on January 20 ‘in response to Mr Sinclair making staff at the home aware of his intention to go to Dignitas’.

A spokesman added: ‘Due to the police investigation we cannot comment any further.’